Diagnostic Imaging in Veterinary Dental Practice

Lindsey A. Schneider Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

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Santiago Peralta Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853.

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History and Physical Examination Findings

A 10-year-old 5.4-kg (11.9-lb) spayed female Miniature Poodle was evaluated at a veterinary teaching hospital because of a nonhealing, extraoral draining tract that was first noted as a swelling on the dorsum of the nose 5 months prior to referral. Previous treatments implemented by the referring veterinarian included extractions of selected premolar teeth and courses of orally administered enrofloxacin and orbifloxacin. Despite ongoing antimicrobial treatment, the swelling had progressed to a persistent draining tract.

Pertinent physical examination findings included a percutaneous draining tract approximately 2 mm in diameter located on the dorsal aspect of the nose immediately left of the midline (Figure 1). No signs of systemic disease were detected on general physical examination, although the clients reported that the dog had a history of chronic kidney disease. Dental examination revealed moderate generalized gingivitis as well as several missing premolar teeth consistent with the history of dental extractions. Additional findings included tooth wear with exposed discolored dentin on the distal aspects and tips of all canine teeth and incisive edges of all incisor teeth present, without pulp exposure (Figure 2). The wear pattern suggested abrasion and tertiary dentin formation, possibly attributable to cage-biting behavior.

Figure 1—
Figure 1—

Photograph of the dorsal aspect of the nose of a 10-year-old spayed female Miniature Poodle evaluated because of a nonhealing draining tract (arrow).

Citation: Journal of the American Veterinary Medical Association 243, 6; 10.2460/javma.243.6.783

Figure 2—
Figure 2—

Photograph of the rostral maxillary teeth of the dog in Figure 1. Notice abrasion on the distal aspect of the left maxillary canine tooth.

Citation: Journal of the American Veterinary Medical Association 243, 6; 10.2460/javma.243.6.783

Routine preanesthetic clinicopathologic testing revealed a mildly high BUN concentration (37 mg/dL [reference range, 10 to 32 mg/dL]). Because of the previous history of kidney disease, follow-up urinalysis was planned to be performed by the referring veterinarian. General anesthesia was induced for further dental charting and diagnostic imaging, followed by treatment. A lateral radiographic view of the left maxillary canine tooth was obtained via the bisecting-angle technique1 (Figure 3).

Figure 3—
Figure 3—

Intraoral lateral radiographic view of the left maxillary canine tooth of the dog in Figure 1.

Citation: Journal of the American Veterinary Medical Association 243, 6; 10.2460/javma.243.6.783

Diagnostic Imaging Findings and Interpretation

The intraoral lateral radiographic view of the left maxillary canine tooth (Figure 4) revealed a well-defined periapical lucency approximately 8 mm in diameter, consistent with apical periodontitis.2 No crown fractures were evident, although the area of abrasion on the distal aspect of the left maxillary canine tooth was visible radiographically. An occlusal radiographic projection of the rostral aspect of the maxilla (Figure 5) revealed that the apex of the left maxillary canine tooth was relatively short and blunt, compared with that of the contralateral tooth, consistent with inflammatory root resorption.3

Figure 4—
Figure 4—

The same radiographic view as in Figure 3. Notice the well-defined periapical lucency of the left maxillary canine tooth (black arrows) and the abraded area at the distal aspect of the same tooth (white arrows). A retained root fragment is visible in the region of the mesial root of the third maxillary premolar tooth (black arrowhead); no radiographic signs of inflammation are evident in the region of the fragment.

Citation: Journal of the American Veterinary Medical Association 243, 6; 10.2460/javma.243.6.783

Figure 5—
Figure 5—

Intraoral occlusal radiographic view of the rostral aspect of the maxilla of the dog in the previous figures. The root of the left maxillary canine tooth appears short, and the apex appears blunt (arrow), compared with the contralateral tooth. Notice the widened periodontal ligament space in the apical region of the left maxillary second incisor tooth (asterisk), suggestive of endodontic disease.

Citation: Journal of the American Veterinary Medical Association 243, 6; 10.2460/javma.243.6.783

Additional radiographic findings included multiple retained roots in the maxillary premolar tooth areas bilaterally with no associated signs of inflammation. Furthermore, on the occlusal radiographic view of the rostral aspect of the maxilla, the periodontal ligament space at the apical area of the left maxillary second incisor tooth was widened, suggestive of possible endodontic disease.

Treatment and Outcome

With the patient under general anesthesia after dental charting and imaging, prioritized treatment consisted of a left infraorbital regional nerve block, followed by surgical extraction of the left maxillary canine tooth and curettage of the periapical area via a full-thickness mucogingival flap. Exploration of the periapical region confirmed direct communication with the draining tract on the dorsum of the nose. A sample of periapical tissue was preserved in neutral-buffered 10% formalin solution and submitted for histologic analysis. The flap was sutured in apposition, and evaluation of a postoperative radiograph confirmed that the affected alveolus was completely vacated.

The patient recovered from surgery without complication and was discharged in the hours that followed. Clindamycin hydrochloride (9.3 mg/kg [4.22 mg/lb], PO, q 12 h, for 3 weeks), gabapentin (9.3 mg/kg, PO, q 8 h, for 1 week), and tramadol (2.3 mg/kg [1.05 mg/lb], PO, q 8 h, for 1 week; to be administered if the patient had signs of pain) were prescribed. Plans were made to perform complete periodontal treatment, address the retained root tips, obtain follow-up radiographs, and possibly treat the left maxillary second incisor tooth in staged visits. Eight weeks after surgery, the client indicated that the draining tract had completely resolved.

Histologic evaluation of the submitted periapical tissue revealed an inflammatory lesion with marked infiltrates of nondegenerate neutrophils, lymphocytes, and plasma cells, confirming the diagnosis of apical periodontitis.

Comments

Intra- and extraoral draining tracts are frequently detected in patients with endodontic disease. Draining tract formation is particularly common in dogs with endodontic disease of the canine or maxillary fourth premolar teeth.4

Periapical lucencies are a common radiographic finding in patients with endodontic disease (ie, necrotic pulp) and result from a local inflammatory process that leads to bone lysis.5,6 These lucencies may correspond to the presence of abscesses, cysts, or granulomas; however, the exact nature of a lesion cannot be determined radiographically.7 External inflammatory root resorption results from local osteoclastic activity associated with the periapical inflammatory process.3

Pulp necrosis and associated apical periodontitis can result from direct pulp exposure caused by trauma (ie, complicated fractures), caries, or tooth resorption.5 Although direct pulp exposure is one of the most common causes of pulp necrosis in dogs,4 indirect exposure (ie, dentin exposure) can lead to similar consequences.5

When dentin is exposed, odontoblasts usually secrete tertiary dentin, increasing dentin thickness as a compensatory mechanism to protect the pulp.8 If abrasion occurs at a rapid rate, it can exceed the rate of tertiary dentin formation and result in pulp exposure. Tertiary dentin often appears discolored and can be clinically distinguished from pulp exposure by use of a dental explorer.

Dentin contains millions of dentinal tubules; if exposed, these tubules can allow irritants and bacteria to penetrate the pulp cavity, possibly leading to pulpitis, pulp necrosis, and apical periodontitis.5 Causes of dentin exposure include uncomplicated fractures and tooth wear from abrasion and attrition. Because the diameter of dentinal tubules gradually increases as they approximate the pulp cavity,8 the closer exposed dentin is to the pulp, the greater the possibility of irreversible pulp damage.

Apical periodontitis occurs secondary to pulp injury because inflammatory mediators from infected or inflamed pulp tissues induce osteoclastic activity, leading to loss of bone around the root apex.5 Treatment options for endodontically compromised teeth include root canal treatment or extraction. Endodontic treatment in dogs generally carries a good prognosis, with a failure rate as low as 6%.9 The presence of a preoperative periapical lucency and inflammatory root resorption are considered risk factors for failure of root canal treatment but not a contraindication for this treatment.9 In light of the clinical and radiographic findings for the dog of this report, a 2-visit root canal treatment could have helped increase the chance for success10 if this option had been pursued.

The findings for this patient suggest that dental abrasion and attrition are indications for intraoral radiography, even in the absence of obvious pulp exposure or other clinical indicators of endodontic disease. Intraoral radiography is essential for the diagnosis of endodontic disease and is a useful tool in determining prognosis and formulating an adequate treatment plan.

References

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  • 8. Luukko K, Kettunen P, Fristad I, et al. Structure and functions of the dentin-pulp complex. In: Hargreaves KM, Cohen S, Berman LH, eds. Cohen's pathways of the pulp. St Louis: Mosby Elsevier, 2011;452503.

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  • 9. Kuntsi-Vaattovaara H, Verstraete FJ, Kass PH. Results of root canal treatment in dogs: 127 cases (1995–2000). J Am Vet Med Assoc 2002; 220: 775780.

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  • 10. Vera J, Siqueira JF Jr, Ricucci D, et al. One-versus two-visit endodontic treatment of teeth with apical periodontitis: a histobacteriologic study. J Endod 2012; 38: 10401052.

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